Since the last blog post on US FDA guidance on software classification, things evolved quickly with the FDA. We know where they want to go with software as medical device, but not exactly how they will implement it.
Let's do a review of what has been done since the publication of the 21st Century Cures Act.

This article is the last of three articles which deal with the concept of
"inflation" of medical devices. The first
one was on inflation of standards, the second
about inflation of regulations. This one, the most interesting to my eyes, is
about multiplication of apps on mobile devices, especially smartphones and
tablets.
More that 6000 apps are classified in the "heath", "heathcare" or "medical"
categories of the Apple or Android appstores. Many of these apps are classified
as medical devices and are in the scope of regulations like FDA and CE Mark.
Note that some apps may be regulated the FDA but not the CE Mark or
vice-versa.

The GHTF (Global Harmonization Task Force) issued a draft of a new guidance on medical
device classification They recommend to implement four classes for medical
devices based on intended use: from class A (lowest risk) to class D (highest
risk). And they give a set of rules on how to choose the classification of the
devices.

Comparison with regulations

Wait, I've already seen this elsewhere. Classification of devices in Europe
(CE mark) and in Canada have systems very similar to what GHTF recommends. This
is a good thing to have an ongoing harmonization process. National regulations
copy what GHTF recommends and GHTF copies what national regulations require.
This is a virtuous circle. Maybe one day the FDA will implement this
classification system.